1. Field of the Invention
This invention relates to motorized winding and rewinding cameras in which a roll of film is wound and rewound by a built-in motor.
More particuarly it relates to a camera in which the buit-in motor is brought into operative connection with a driving torque transmission for winding the film in automatic response to completion of film rewinding.
2. Description of the Prior Art
Recently, "full automation" has occurred particularly in the field of leaf shutter type (medium priced) cameras, and this trend is spreading to the field of single lens reflex cameras. The term "full automation" as herein used implies that as is well known, not only the exposure operation as a matter of course, but also all other operations including film winding and focusing and further even the film rewinding in sequence to the finish of film feeding, are automatically carried out by the electric motor incorporated in the camera housing, thus freeing the photographer from the distraction of carrying out a troublesome sequence of operations so as to enable the achievement of good photographs. Of the above-described various operations, with regard film rewinding automatization, certain points enumerated below must be taken into account particuarly in a camera in which the electrical circuitry and mechanisms are so designed that after the last available film frame has been exposed, the photographer needs to manually perform switching from the winding to the rewinding mode by an actuator accessible from the outside of the camera;
(1) The actuator must be provided with a foolproof means for preventing an unintentional operation of the actuator before the roll of film is all exposed; and
(2) If the photographer forgets to return the actuator to the initial or "winding" position after the exposed roll of film had been rewound and the film cartridge is unloaded, the camera after having been loaded with a new cartridge will not advance the film when the shutter button returns from the depressed position. Such a situation has sometimes been taken as an indication that the camera is broken.
With regard to the above-described first point (1), it has been known in the prior art to provide for the rewind control member with a cover or a lock mechanism. Another way is to construct the rewind control actuator in two parts which have to be operated in sequence. At any rate, principally the prior art when effecting switching to the rewinding mode there are involved two or more steps of operation.
To solve the problem described in connection with the second point (2) mentioned above, the following different methods have been employed:
(a) The rewind control actuator is biased by a spring so that the photographer is required to retain the actuator in the rewinding position against the spring all the while the rewinding goes on. Upon knowledge of the finish of rewinding by means of a change of the motor sound, or by an exterior monitor which blinks so long as the film moves, the photographer will then remove his finger from depressing the actuator, whereby the actuator is automatically returned to the initial or winding position.
(b) Since continuous holding of the rewind control actuator with the finger is quite laborious, in accordance with another method the actuator after having been switched manually to the rewinding position is mechanically held in that position. When rewinding is completed, the motor is automatically stopped, and at the same time a visual or acoustic signal in the form of a light from an exterior indicator lamp or a sound from buzzer is emitted rewinding the photographer to return the actuator to the initial or winding position.
(c) in accordance with another method, unloading of the camera is mechanically hindered in such a manner that the back cover cannot be opened, or the exposed film cartridge cannot be taken out of the chamber in the camera, until the photographer resets the rewind control member to the winding position.
All of these prior art methods, however, require the photographer either to manipulate or to watch some of the operating members on the camera. In the present state of art, therefore, the photographer cannot relax his hands after the camera has been switched to the rewinding position until a new film cartridge is properly loaded and the camera operates in the winding mode. This can hardly be said in a true sense to be automatic rewinding.